Submission to Modify the Australian Yachting Federation Special Regulations Part 1, Appendix D Resistance to Capsize

Transcription

1 Submission to Modify the Australian Yachting Federation Special Regulations Part 1, Appendix D Resistance to Capsize Prepared by Richard Slater PO Box 800, Mona Vale NSW 1660 Phone: Mobile: +61 (0)

2 SUMMARY OF SUBMISSION The main reasons for including a limit on a boat s static angle of heel are no longer valid. A Static Angle of Heel Rule fails in its purpose to make boats resistant to capsize. The only true test available of a boat s resistance to capsize is its limit of positive stability and its stability analysis. There is no reference made to limit of static heel in the latest ISAF Special Regulations (from which the AYF bases its Special Regulations). The ISAF Special Regulations offers guidance notes and recommendations in regards to resistance to capsize. These notes only discuss stability indexes and the soon to be published ISO standard. Rules need to be amended so that all boats, not just boats with moveable / variable ballast should comply with the appropriate stability limit in their least stable configuration. This will cover other design ideas that are making their way into the sailing community. Boats with moveable / variable ballast can and do achieve ISAF Category 0 specifications regarding stability, let alone category 1. Since the current AYF special regulations were released in 2001 there have been 2 amendments made to them. Therefore a precedent is there for making a change to Appendix D now, rather than waiting for the new Special Regulations to take effect in July 2004.

3 BACKGROUND TO THE SUBMISSION Australian Yachting Federation Special Regulations, Part 1 Appendix D relates to assessing how monohull boats are resistant to capsize. So when is a boat capsized? RRS 21 states: CAPSIZED, ANCHORED OR AGROUND; RESCUING If possible, a boat shall avoid a boat that is capsized or has not regained control after capsizing, is anchored or aground, or is trying to help a person or vessel in danger. A boat is capsized when her masthead is in the water. This explanation of capsize is not intended to be the definition of what it is to capsize, if it was intended to be a definition within the Racing Rules of Sailing, capsize and its meaning would be included as a Definition. I propose that consideration must also be given to the ability of a boat to re-right itself after being inclined to extreme angles. This might include angles beyond when a masthead is in the water. The AYF s Special Regulations - Appendix D is intended to provide prescriptive tests to determine a boats resistance to, and recovery from capsize. The AYF Appendix D.3 provides 4 methods to determine any boats resistance to capsize. Each of these methods is an attempt to determine a boats righting moment and then D.4 provides a minimum requirement based on the applicable test and type of race. Any boat with moveable / variable ballast must satisfy the stability tests as provided in D.3 but in addition, must also satisfy 2 other requirements: D.2 Static Angle of Heel and D.1.01 keeping on board a written declaration from the designer and IMS measurer. It is the Static Angle of Heel requirements that this submission questions. This submission also attempts to suggest suitable alternative arrangements to deal with the range of new designs appearing in the sport. The appearance of yachts with canting keels has stirred debate in Australian yachting circles; with many people misunderstanding the rules and issues that currently govern boats with moveable ballast. Yachts with canting keels are legal in Australia when raced under IRC. There is no safety rule that specifically prohibits canting keel yachts. It is the fixed limit of 10 degrees of static angle of heel that many of the canting keel yachts fail to satisfy and it is the static angle of heel requirement that is being questioned in this submission.

4 PROPOSED CHANGES TO APPENDIX D: Below are the relevant parts of Appendix D as well as suggested modifications. The text in italics and underlined is proposed additions to the existing rule and proposed deletions are struck through. APPENDIX D RESISTANCE TO CAPSIZE FOR MONOHULLS D.1 RESISTANT TO CAPSIZE To be considered Resistant to Capsize as required in Regulation 3.02 and as defined in Regulation 1.03 boats shall be assessed as follows: D.1.01 BOATS WITH MOVABLE / VARIABLE BALLAST, apart from boats having only a Centreboard or Drop keel on the centreline of the hull, shall comply with Sections D.2 and D.3 below and shall keep on board a copy of a written declaration from the designer stating that the boat complies with Sections D.2 and D.3 below, one from the IMS measurer who conducted the Inclination stating the Static Angle of Heel and one from the builder declaring that the boat was built to the declared design. Any alterations made to the boat that might effect its stability invalidates the original declarations which must then be renewed. Organising Authorities may request to see these declarations or require copies of them before accepting an entry from the boat. D.2 BOATS WITH MOVABLE BALLAST D.2.01 D.2.02 Static Angle of Heel With all movable ballast moved to the most extreme position on one side the angle of heel shall not exceed 10 degrees. Inclination To determine the Static Angle of Heel, boats with movable ballast, apart from having only a Centreboard or Drop Keel on the centreline of the hull, shall be inclined. When all the ballast is moved from one side to the other the change in angle of heel shall not exceed 20 degrees. Boats shall be measured in normal sailing trim which shall be as defined in IMS Rule 402.2(1999) but excluding the first sentence of clause (h). D.3 RESISTANT TO CAPSIZE When determining the boat s resistance to capsize, the designer must be able to show that the boat satisfies the requirements in it s least stable configuration (the configuration that most reduces the righting moment) To be considered resistant to capsize all boats shall have a minimum satisfactory righting moment. This shall be determined by any one of the following methods. IMS Measured Boats may use the Stability Index limits set out in IMS Regulation 201. IRC Measured Boats may use the SSS Numeral and the limits set out in the RORC IRC Booklet. (cont )

5 WHY THE 10 0 STATIC HEEL RULE WAS INTRODUCED To understand why the 10 degree static heel rule should be removed, you only need to look at why the static heel rule was included in the first place. The 10 degree static heel requirement under AYF Special Regulations - Appendix D.2 was first included in the Special Regulation Rules edition. Prior to this edition of the AYF Racing Rules, a boat was considered to be resistant to capsize if under IMS she had a Stability Index that was above the limit set for the particular race; or if not an IMS measured boat, the boat achieves the RMI or Horizontal Stability Factor set out for the particular race category. In the edition, the 10 degree static heel rules (D.2) were included based on 2 main reasons: 1. The Channel Handicap System (precursor to the IRC) had wording that was interpreted to limit boats in IRC to a 10 degree static angle of heel. 2. A 10 degree static heel rule (and 20 degree change in angle with ballast moved from side to side) was similar to the International Monohull Open Class Association (IMOCA) stability rule. Let us therefore review these 2 main reasons for inclusion of a static heel test from what we know today.

6 1. 10 degree static angle of heel limit in IRC. Below is the wording from IRC rule prior to its recent change in November 2002: Before issuing a certificate, the rating authority may require evidence that with all ballast tanks on one side of the boat filled, or with movable ballast moved fully to one side, the boat does not heel by more than 10 degrees when in the Empty Weight condition (see Rule 22.0). The AYF interpreted this rule to mean that no boat can have a static angle of heel of more than 10 degrees. Given that at the time of preparing the edition of the rules IMS did not allow moveable ballast, it was logical to include this limit of 10 degree static heel into the AYF special regulations as it was considered to mesh with the IRC rule. In July / August 2002 the issue of static heel was raised with the application for and subsequent issue of an IRC rating certificate for Wild Oats, a boat with a static angle of heel greater than 10 degrees. RORC issued the certificate based on the fact that the rule is permissive over whether or not a boat must not have a static angle of heel greater than 10 degrees. The key word in the rule being may. This issue was raised at the September 2002 IRC Council Meeting in Southampton 1. The result is that the IRC rule is not intended to limit boats to 10 degrees static heel, rather that the rating office wanted the right to review those boats who had moveable / variable ballast that resulted in the boat going above the 10 degrees static heel. However, in recognising the ambiguous wording of the IRC rule on this issue, the IRC council re-worded the rule to be clearer. The resulting change to IRC is: There is no limit to the static heel angle with ballast tanks fully filled on one side of the boat or with movable ballast moved fully to one side. For boats with water ballast, the maximum weight of water that can be carried on each side of the boat shall be declared. For boats with moveable ballast, the maximum static heel angle in the Empty Weight condition (see Rule 22.0) with the ballast moved fully to one side shall be declared. The re-worded rule leaves no doubt that this international rating rule allows boats to have a static angle of heel greater than 10 degrees. This also suggests that one of the two main reasons for the AYF to impose a static heel limit was based on an incorrect assumption. 1 A copy of the IRC Council Minutes can be found in appendix 1. The relevant sections of the minutes are point #9 found on page 6 of the minutes and the Report to the Council by Mike Urwin on pages

7 2.1 IMOCA s use of the Static Angle of Heel as a test of a boat s resistance to capsize. The other main reason for the static angle of heel rule to be included in the AYF special regulations stemmed from the fact that it was a rule that has been used in the International Monohull Open Class Association (IMOCA) 2 for some time. Open Class boats must conform to a rule where the combined angle of heel must not exceed 20 degrees when the moveable / variable ballast is shifted from the extremes of one side to the other. In order to still maximise the high righting moment gained from moveable / variable ballast, boats are designed and built extremely wide (greater form stability) in order to satisfy the angle of heel rule. The design parameters resulted in boats that are designed to sail with heel angles of 15 to 20 degrees The result is a class of boats that during their development proved to be very stable when inverted (capsized). In a Seahorse article (May ) it was calculated that some older Open class boats required 40 to 50 degrees of heel to re-right themselves once inverted. This is after they have satisfied the 10 degree static angle of heel rule. In an ISAF meeting in September 1997 organised to review Open Class safety, Groupe Finot (designers of many winning Open class boats) presented a paper to the meeting on security of Open 50 footer and 60 footers. 4 An Open 60 during its inversion test. Experience shows that water ballasted / fixed keel boats can take up to 2 hours to right themselves from this test (usually involving flooding the front compartment of boat and the ballast tanks on one side) Many Open class canting keel yachts over-cant their keels to one side (to an angle where they would no longer satisfy the 10 degree static heel limit) and the boat rights itself in seconds. 2 The relevant IMOCA rules governing Stability are contained in Appendix 2 (section E of the rules). 3 A copy of the Seahorse article can be found in appendix 3. 4 Copies of presentation outline, refer to

8 Part of their paper was on stability and the ability of an Open class boat to re-right itself after being inverted. Their recommendations on how to make the Open class boats more likely to re-right after being inverted were: 1. The moderated width of the boat 2. The volume of superstructures 3. The tightness of the mast 4. Flood ability 5. The canting keel 6. The inflation of volume Moderating the beam of the boats will assist in their ability to recover from being inverted (the most extreme of predicaments) but the class rule that limits static heel has proven that designers are forced to increase beam, in order to satisfy the static heel requirement. In the Open class, designers have now learned the need to look at the Limit of Positive Stability (LPS) as a key tool in determining a boat s resistance to capsize. The class has now moved to including a high Limit of Positive Stability (called in the IMOCA rule Angle of vanishing stability, or AVS) of degrees. In preparing this submission, contact was made with Merfyn Owen (Owen Clarke Design). Merfyn Owen has been active in design and project managing various Open 50 and 60 boats (including Kingfisher for Ellen MacArthur and Hexagon for Graham Dalton). When asked of the origin of a static angle of heel rule in the IMOCA class, Merfyn stated: This rule was instigated by the Royal Western Yacht Club who were the Organisers of the OSTAR and TWOSTAR events in the early eighties. They included this rule as a direct response to the boat Thursday's Child in an effort to restrict the amount of water ballast that a yacht could load and hence increase it's INITIAL STABILITY, whilst undermining it's ultimate stability. Furthermore, Merfyn Owen believes that the reason the static heel limit still exists in the IMOCA rules is to stop existing designs becoming obsolete. For Open 50 and 60 s, Merfyn Owen believes that the negative design trends this rule encourages are now offset by the introduction of a minimum AVS. As such there is a good compromise in the fleet now with existing boats still being able to be raced around the globe with the knowledge that in the event of a major knockdown the boats will be self righting (by way of canting keels and a high AVS).

9 2.2 Other Class and their use of the Static Angle of Heel as a test of a boat s resistance to capsize. While it is important to remember that rating rules have a primary function of providing a basis for different designs to race against each other, all rating rules include the premise of producing boats that are safe. This means that rating rules should not be considered the last word on safety; rather the different rules can be used as a guide on how to assess a boat s resistance to capsize. After all, the AYF has chosen the IMOCA rule and incorporated part of that rule when including a limit static heel in its special regulations. IMOCA rules are written to take into account boats that are competing in Category 0 races (trans-ocean) and often singlehanded. This puts different emphasis on designs, for example these boats spend most of their time under autopilot, with its associated dangers. If one rating rule is used to provide methods of determining resistance to capsize, we should also look at other rating rules and their approach. IRC We have already covered IRC s approach to this in the previous section. IMS The International Technical Committee (ITC) of the Offshore Racing Council is currently considering moveable and variable ballast issues and how they can be integrated into IMS. The chairman of the ITC, Mr Manolo Ruiz de Elvira stated From the safety point of view we are interested in a boat being able to resist capsize, not how much it heels. When considering these new designs we need to be conservative in ensuring the safety aspects of the boat. We consider a boat s Limit of Positive Stability (LPS) a reasonable approach on how to judge moveable ballasted boats at this time. The ITC is reviewing all aspects of moveable / variable ballast design before making a more definitive policy. The next ITC meeting will be held at the end of May. One item for discussion is the limit of static heel and its use in considering a boat s resistance to capsize. I hope to have the minutes of that meeting available for review as soon as they are released.

10 Volvo Ocean 70 Volvo has made an enormous investment in the Volvo Ocean Race and as with all their marketing ventures they wish the Volvo Ocean Race to be seen as a safe adventure. When asked if the new Volvo 70 rule will include a static heel limit, James Dadd, the class measurer involved with the formulation of the new Volvo 70 rule surmised 5 : It is therefore recognised that, whilst the static heel angle is intended to increase safety, it in fact reduces the safety factors significantly. As such it has been unanimously agreed that the new Volvo Ocean 70 class will not include any static heel angle limits. Instead it will limit the angle the keel may cant relative to the hull and include an inverted stability test. Concept of New Volvo Race Boat Image Owen Clarke Design 5 See Appendix 4 Memo from James Dadd outlining Static Heel Angle restrictions for the VO 70 rule.

11 Extremely wide Open 60 s, designed with the IMOCA static stability rule partially in mind. The New RP CBTF 60 Wild Oats. This boat has a static heel greater than 10 degrees and is able to race Cat 1 races overseas, qualifying under SSS Numeral and STIX (ISO 12217)

12 HOW SHOULD ONE JUDGE RESISTANCE TO CAPSIZE? Quantifiable guides to stability are already outlined in Appendix D.3. The AYF set out specific requirements for all boats to be considered resistant to capsize. Each category (1 to 6) has a minimum requirement for a boat based on (up to) 4 different methods used to determine a minimum satisfactory righting moment. These 4 methods are: IMS measured boats may use the Stability Index limits as set out in IMS Regulation 201. IRC measured boats may use the SSS Numeral and the limits set out in the RORC IRC booklet. Unmeasured boats may use the RMI or the Horizontal Stability factor. Boats competing in Trailable boat races shall use the Horizontal Stability factor. The suitability of these methods (in particular the IMS and IRC methods) have been tested and gained international acceptance. In the CYCA s Report of the 1998 Sydney to Hobart Yacht Race, Andrew Dovell, from Murray, Burns & Dovell Naval Architecture and Composite Engineering, made a submission that included review of stability standards. In making recommendations on stability, Andrew Dovell stated: 4. Given the close correlation between a yacht s limit of positive stability and the amount of time it will remain inverted before being righted, there is little impetus to take this research any further. It may however be useful to study the implications of the amount of time a yacht is inverted once rolled in terms of it s ability to remain self sufficient once back upright. This study may have a bearing on the limit of positive stability set for future Sydney to Hobart Races. What comes out from this paper is the fact that the IMS Stability Index (in the Andrew Dovell case) provides an objective assessment of stability The recommendations of the 1998 Sydney to Hobart Yacht Race Review committee were that all boats would need to conform to the IMS stability recommendations for Cat 1 Races of 115 degrees 6. This was the only recommendation in regards to a boat s resistance to capsize. 6 Refer Report of the 1998 Sydney to Hobart Yacht Race May Page 154

13 In the NSW State Coroner s Inquest into the 1998 Sydney to Hobart Yacht Race, Mr John Abernathy made the following findings in regards to stability: 2. Relying on the experiments of Dr. Renilson I find:- (a) That the lower a vessel's limit of Positive Stability the more susceptible it is to being knocked down and being inverted; (b) In general the higher a vessel's limit of Positive Stability the sooner it will be righted from the inverted position; (c) Because of the different deck configurations of vessels no recovery time from the inverted position can be accurately predicted for any limit of Positive Stability. (Page 160) It is clear that the limit of positive stability was considered in the coroner s report the key determinant to a boats ability to resist capsize. On an international front, the adoption of the STIX 7 and AVS by IRC and IRM as a figure on the rating certificate (in addition to the SSS Numeral) is a sign of overseas bodies moving to an internationally recognised test of stability as a guide to a boat s resistance to capsize. The use of STIX in Australia is limited at this time. Mainly because the highest level STIX (design category A) has the following parameters: Wave height: up to approx 7 m significant (highest 1/3 rd of waves) Typical Beaufort wind force up to 10 Calculation wind speed (m/s) 28 When considering many Ocean Races include sailing in Southern Australia / Bass Straight these parameters seem low. One option that we have canvassed to RORC is the possibility that a design category can be set with the above variables increased. However this discussion is separate to this submission. 7 STability IndeX. A new international standard for the stability and buoyancy of boats.

14 STABILITY OF BOATS WITH MOVEABLE BALLAST In a paper on Limits of Positive Stability 8, Mr Christopher Murman from Floating Pointz Designz in Mosman gives examples of GZ curves for a typical hydrostatic curve and extrapolates from the curves what it means for the boat. In the example above, at the point of 129 degrees the boat is said to be in equilibrium, that is, given no other external forces, the boat would remain in that position ( a hypothetical concept because even one small ripple should cause the boat to move away from equilibrium). It is considered that once the curve becomes negative, it is said that the boat is stable in an inverted position. 8 Copy of the Paper in Appendix 6.

15 If we consider a canting keel boat and review the GZ curve. Reichel Pugh Yacht Design has been kind enough to release studies they have produced in regards to the GZ curves of a 60 foot Canting Ballast, Twin foil boat 9. With the keel locked in the centreline, the GZ curves have the same similarities as conventional fixed keel boats. However it is interesting to consider the boat when its keel is canted fully to leeward. The first issue that is different is that when the righting arm is negative, the boat is not necessarily stable upside down as was the premise when viewing a typical GZ curve. Negative righting arms in this example simply show that the heeling force is acting in the opposite direction. For example, when the keel is canted to leeward, the boat wants to heel to 28 degrees. Therefore there is a force that is required to act on the boat to attain a 0 degree static heel. From 0 to 28 degrees that force is in the opposite direction (counter clockwise) to the force required to heel the boat from 28 degrees and higher. 9 See full report in Appendix 7.

16 To fully understand the impact of a static heel limit on moveable ballast boats it is important to consider the possible design outcomes that could result from compliance with a 10 degree static heel limit. In the following examples, Reichel Pugh has designed boats to fit within the 10 degree static heel rule. The boats in this study have the following characteristics: Equal Lengths Equal Displacements Equal Vertical Center of Gravity Equal Keel Draft Equal Cant Angle (40 deg) Wide Boat has 15% more hull surface area, 39% more deck surface area and 23% more wetted surface area. One boat satisfies the 10 degree static heel limit by reducing the cant of it s keel to 18 degrees off centre. The other boat is a wide beam boat (similar design concept to satisfy the static heel limit as we see in IMOCA boats). Wide Boat (complying) and Narrow boat (static heel in excess of 10 degrees): INVERTED STABILITY RANGE Wide Boat: 137 to 252 (115 degrees) Narrow Boat: NONE

17 Narrow Boat Limited Keel Cant: Inverted Stability Range 154 to 230 (76 degrees) These plots are then a comparison of a well built narrow boat compared to a wide boat that would have impossibly low structural weight and VCG. In reality the wide boat would: Have more structural weight and less bulb weight, for constant displacement. Have a vertical centre of gravity significantly higher. Have significant increase in its range of inverted stability and decrease in its upright righting arm values. With realistic VCG the wide boat would have the following values: Compare with "Fully Canted to Windward" stability curve. Righting arm at 30 deg heel = 1.40 m (1.80 m on plot). Righting arm at 160 deg heel = m (-1.80 m on plot). Inverted stability range = 150 deg, (116 deg on plot). The plots show that this unrealistically advantaged wide boat still has a significant range of inverted stability. Even with the keel canted to 40 deg the boat would need further assistance to self right, shifting of water ballast etc.

18 In their first study, Reichel Pugh used the same hull parameters but compared boats where the keel cant is reduced in order to satisfy the current 10 degree static heel rule. Below is a summary of the results: Keel Position Range of positive stability LPS (1) STIX (2) IMS Stability Index (3) O Cant Cant to windward (10 static heel) 40 Cant to windward (max canting angle) 18 Cant to leeward (10 static heel) 40 Cant to leeward (max canting angle) (1) The limit of positive stability should be equal to the range of positive stability if measured from the actual beginning of the positive range. In this table, the LPS shown is measured from 0 deg. heel (2) STIX (ISO ) FDIS Version. (3) Precise value yet to be corroborated, question due to complexity of calculation of IMS LPS vs Naval Architecture LPS. The results in this instance show a boat that satisfies worldwide standard of stability to race in ISAF Offshore Special Regulations - Category 1 races. It is pertinent to review the latest version of the Offshore Special Regulations (version 3.19) as it is these Special Regulations that the AYF Special Regulations are based 10. The difference is that the ISAF regulations are updated annually where as the AYF regulations are printed as part of the 4 year rule cycle. The latest version of the ISAF Offshore Special Regulations (v3.19) states: Stability monohulls Either with, or without, reasonable intervention from the crew a yacht shall be capable of self-righting from an inverted position. Self-righting shall be achievable whether or not the rig is intact A yacht shall be designed and built to resist capsize. 10 See page 125 of the AYF RRS. Based on the ORC Special Regulations

19 (ability to re-right from inverted) is to be satisfied for monohull boats competing in Category 0 races while (designed and built to resist capsize) is for monohull boats competing in Category 1 to 4 races. The definition of the ISAF categories is as follows: Category 0 Trans-oceanic races, including races which pass through areas in which air or sea temperatures are likely to be less than 5 degrees Celsius other than temporarily, where yachts must be completely self-sufficient for very extended periods of time, capable of withstanding heavy storms and prepared to meet serious emergencies without the expectation of outside assistance Category 1 Races of long distance and well offshore, where yachts must be completely self-sufficient for extended periods of time, capable of withstanding heavy storms and prepared to meet serious emergencies without the expectation of outside assistance. What can be deduced is that for trans-oceanic races, boats must not only be designed and built to resist capsize, but have an added requirement to be able to be self-righted from an inverted position (able to use reasonable intervention from crew ). The sample 60 foot boat that was used in the Reichel Pugh study clearly satisfies this requirement and therefore satisfies the only ISAF stability rule that only applies to Category 0 (Trans-oceanic) races. This shows that a boat that doesn t satisfy a limit of static heel of 10 degrees can still satisfy the International Sailing Federation s requirements for stability in the highest category available (category 0). In Australian terms, the highest category currently raced are the category 1 races, Sydney to Hobart and the Lord Howe Island Race.

20 SPECIFICS OF THE SUGGESTED WORDING OF APPENDIX D. 1. Removal of requirement for letter from IMS measurer. This submission suggests the following change to AYF Special Regulations Appendix D1.01: BOATS WITH MOVABLE / VARIABLE BALLAST, apart from boats having only a Centreboard or Drop keel on the centreline of the hull, shall comply with Sections D.2 and D.3 below and shall keep on board a copy of a written declaration from the designer stating that the boat complies with Sections D.2 and D.3 below, one from the IMS measurer who conducted the Inclination stating the Static Angle of Heel and one from the builder declaring that the boat was built to the declared design. Any alterations made to the boat that might effect its stability invalidates the original declarations which must then be renewed. Organising Authorities may request to see these declarations or require copies of them before accepting an entry from the boat. Many of the boats with movable / variable ballast will not race, nor rate under the IMS. As our submission is to remove any inclination test from appendix D, there is no need to have any measurer declare that a boat complies with the inclination test. Those boats that are able to use water ballast under IMS will have the fact of the water ballast noted on their certificate and those boats under IRC have the ballast system and static angle of heel noted on the IRC certificate. This submission believes that boats with Movable / Variable ballast should still carry on board a copy of the written declaration from the designer stating that the boat complies with the other rules of AYF Special Regulations Appendix D as well as a declaration from the builder stating that the boat was built to the declared design. This provides a written trail of evidence for Organising Authorities and should circumvent any added administration difficulty when accepting such boats into events.

21 2. Additional paragraph to D.3 (re-numbering required). Below again is the suggested additional paragraph to AYF Special Regulations Appendix D3: RESISTANT TO CAPSIZE When determining the boat s resistance to capsize, the designer must be able to show that the boat satisfies the requirements in its least stable configuration (the configuration that most reduces the righting moment) The intent of this paragraph is to catch all current and future design innovations and ensure that in whatever configuration of sailing, they satisfy the stability indicators as required by AYF Special Regulations Appendix D. The wording also moves away from the issue of movable / variable ballast and can take into account design innovations such as canting masts. It is arguable that canting masts would not be measured in different positions when looking at a boat s stability under the current rules based on the fact that masts are not considered ballast. The wording also takes into account stacking. This is where class rules allow sails and other dead weight to be moved about the boat for the purposes of increasing trim. This is prevalent in the Volvo 60 class. Under current rules, a Volvo 60 s resistance to capsize is not calculated with stacking taken into account, nor any water ballast held. It does, however have a dry range of positive stability limit of 142 degrees and specifies some weight positioning 11. This additional paragraph can also apply if the concept of Ultimate Stability is adopted. It means that a boat cannot be loaded with crew above what a design intended for. 11 VO 60 Class Rule 7.2.2